Bond clevage

Bohr relationship, 95 Boltzmann distribution law, 51, 52 Bond clevage, Norrish Type I, 238 Norrish Type II and III, 240 Bond dissociation energy, 6 Bond length, 29, 93 Born-Oppenheimer approximation, 29, 97... 

Angelici and coworkers recently disclosed an interesting photochemical reaction of RcjlCO), with BT (Eq. 4.16) that produces a C-S bond clevage product containing a bridging ring-opened BT, of similar stmcture to those described in Eq. 4.2 for Co and in Fig. 4.9 for Ni. Upon addition of excess PMcj two different phosphine substitution products are formed in one of which both the C-S and the Re-Re bonds have been cleaved [59]. 

Excited states associated with metal-metal bonded complexes. Other types of decay mechanisms are found from excited states of organo-metallic compounds having direct metal-metal bonds. Iradiation of dinu-clear and trinuclear metal-metal bonded complexes leads to efficient metal-metal bond clevage generating highly reactive mononuclear frag-... 

In an effort to obtain a salvinorin derivative possessing an oe-diol system which can be transformed into the dibenzoate ester required for the exciton chirality CD method, salvinorin A (1) or B (2) was treated with sodium borohydride in various protic solvents. The products having the la,2a-diol group were obtained in high yield. However, this reduction was accompanied by extensive isomerization at C-8. While mechanistic details for this unexpected observation remain to be established at this time, the isomerization at C-8 appears to be the result of the base-promoted clevage of the C-8/9 bond under the reaction conditions followed by the reclosure to provide the 8-epimer prior to the reduction of the 1-ketone. Furthermore, attempts to obtain the 1,2-dibenzoate derivative of the major reduction product 3 under various benzoylating conditions invariably produced only the 2-monobenzoate. 

With the exception of the low temperature studies mentioned earlier, mechanistic details of cyclobutenedione reactions have not yet been investigated. The products clearly indicate that clevage of the intercarbonyl bond is the major reaction of excited state(s). Interestingly, there is no evidence for a primary process involving formation of a triple bond and carbon monoxide (or C202). 

Tertiary C—H bonds show the highest reactivity. However, protolytic cleavage of tertiary and secondary nitroalkanes is a major side reaction, and can lead to the formation of a variety of byproducts. Protolytic denitration was demonstrated by reacting 2-nitro-2-methylpropane with FSOjsH-SbFi, HF-SbFs, and HF-PF5 at -80 C. The protolytic clevage reaaion yields r-butyl cation and nitrous acid (or subsequently, nitrosonium ion). 

Phosphonous diamides can be prepared by clevage of the Si-N bond in amino silanes by reaction with phosphonous dichloride (Figure 7.4). 

Igudii, K., Kaneta, S., Nagaoka. H and Yamada, Y. (1989) Synthesis of clavulone derivatives selective clevage of ester bonds in clavulone. Chem. Lett., 157-160. 

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